Follicle stimulating hormone (FSH) and luteinizing hormone (LH), sometimes referred to as gonadotropins or gonadotropic hormones, are released by the pituitary gland which is attached by a stalk to the region in the base of the brain known as the hypothalamus. These hormones, in combination, regulate the functioning of the gonads to produce testosterone in the testes and progesterone and estrogen in the ovaries, and they also have other biological functions.
Hormone release by the anterior lobe of the pituitary gland usually requires prior release of hormones produced by the hypothalamus. A hypothalamic hormone which triggers the release of the gonadotropic hormones, particularly LH, is generally now referred to as GnRH. GnRH was isolated and characterized as a decapeptide some 25 years ago. Shortly thereafter, it was found that analogs of GnRH having a D-isomer instead of Gly in the 6-position have greater binding affinity/strength to the receptor and greater biological potency than the native hormone; one example is D-Ala.sup.6 !-GnRH (U.S. Pat. No. 4,072,668) having the following formula: pGlu-His-Trp-Ser-Tyr-D-Ala-Leu-Arg-Pro-Gly-NH.sub.2.
The formula for the GnRH analog represented above is in accordance with conventional representation of peptides where the amino terminus appears to the left and the carboxyl terminus to the right. The position of each amino acid residue is identified by numbering the amino acid residues from left to right. In the case of GnRH, the hydroxyl portion of the carboxyl group of glycine at the C-terminus has been replaced with an amino group(NH.sub.2) i.e. the C-terminus is amidated. The abbreviations for the individual amino acid residues above are conventional. Except for glycine, the amino acids and other modifiers attached thereto set forth hereinafter should be understood to be of the L-configuration unless noted otherwise to be the D-isomer.
The administration of GnRH analogs that are antagonistic to the normal function of GnRH has been used to suppress secretion of gonadotropins generally in mammals and to suppress or delay ovulation. Because GnRH antagonists are capable of immediate inhibition of pituitary gonadotropin secretion by competing with the stimulatory effect of endogenous GnRH, such analogs of GnRH are being investigated for their potential use as suppressives, as contraceptives and for regulating conception periods and for the control of the timing of ovulation for in vitro fertilization. For example, GnRH antagonists may be used for the treatment of precocious puberty and endometriosis and other such conditions which result from hypersecretion of gonadotropins, and they are also useful for regulating the secretion of gonadotropins in male mammals, where they can be employed to arrest spermatogenesis, e.g. as male contraceptives, for treatment of male sex offenders, and for treatment of prostatic hypertrophy. GnRH antagonists are also used to treat steroid-dependent tumors, such as prostatic and mammary tumors. In the female, they can also be used to treat hirsutism. GnRH antagonists offer advantages over the currently available, lengthy administration regimen of GnRH agonists, such as the absence of an initial gonadotropin stimulation (flare) and the dose proportional efficacy.
The development of these compounds has been hampered by histamine-release inducing properties, i.e. cause histamine to be released from mast cells which cells are found in the skin, the gingiva and other locations throughout the body. As a result, inflammation is caused, at times resulting in edema of the face and elsewhere on the skin. Certain GnRH antagonists that are effective in preventing ovulation have the undesirable adverse side effect of stimulating histamine release; thus, the design of GnRH analogs has generally been directed to providing peptides that retain the biological efficacy but do not exhibit such undesirable histamine release, see J. Rivier et al., J. Med. Chem., 29, 1846-1851 (1986). The occurrence of depot formation after injection due to "gelling" results in release from the injection site that may be difficult to control, and improvements in solubility of these peptides have been sought to avoid such gelling.
The aim of GnRH antagonists is generally to suppress endogenous gonadotropins and/or sex steroids, and such suppression may be required for either short periods of time (e.g. during infertility treatment) or for long periods (e.g. during the treatment of endocrine cancers). Depending on the specific indication, short-term treatment varies from 1 day to about 6 weeks, whereas long-term treatment may last from several months to many years. A subdivision in short- and long-term treatment has a practical background. Presently available pharmaceutical formulations of GnRH antagonists permit daily subcutaneous (sc) administration only; therefore, long-acting, sustained-release formulations are required if one is to effect long-term treatment, with such formulations being only in the early stages of pharmaceutical development.
Short-term GnRH antagonist treatment is anticipated to be effective in the following situations:
(1) diagnostic; PA1 (2) prevention of luteinizing hormone (LH) surges in controlled ovarian hyperstimulation (COH) for assisted reproductive techniques; PA1 (3) suppression of increased LH levels during induction of ovulation in polycystic ovarian disease (PCOD) to decrease the incidence of spontaneous abortion; PA1 (4) premenstrual syndrome (PMS); PA1 (5) treatment of threatening ovarian hyperstimulation syndrome (OHSS); PA1 (6) preparation for surgery of leiomyoma; PA1 (7) functional menometrorrhagia; PA1 (8) male contraception by (initiating the) suppression of gonadotropins; PA1 (9) protection of the gonads during cytostatic treatment for cancer; and PA1 (10) interval treatment of endometrial cancer between diagnosis and surgery. PA1 (1) prostate cancer; PA1 (2) breast cancer; PA1 (3) endometrial cancer; PA1 (4) ovarian cancer; PA1 (5) benign prostatic hypertrophia; PA1 (6) precocious puberty; PA1 (7) endometriosis; PA1 (8) hyperandrogenism; and PA1 (9) promotion of hair growth. PA1 X-D-2Nal-(A)D-Phe-D-3Pal-Ser-Xaa.sub.5 -Xaa.sub.6 -Leu-Xaa.sub.8 -Pro-Xaa.sub.10 PA1 X is an acyl group having up to 7 carbon atoms or Q, PA1 Xaa.sub.5 is 4Aph(Q.sub.1) or 4Amf(Q.sub.1) with Q.sub.1 being Q or ##STR2## Xaa.sub.6 is D-4Aph(Q.sub.2), D-4Amf(Q.sub.2), D-Lys(Nic), D-Cit, D-Hci or D-3Pal, with Q.sub.2 being For, Ac, 3-amino-1,2,4 triazole, or Q.sub.1 ; PA1 Xaa.sub.8 is Lys(ipr), Arg, Har, Arg(Et.sub.2) or Har(Et.sub.2); and PA1 Xaa.sub.10 is D-Ala-NH.sub.2, NHCH.sub.2 CH.sub.3, Gly-NH.sub.2, AzaGly-NH.sub.2, Ala-NH.sub.2, Agl-NH.sub.2, D-Agl-NH.sub.2, Agl(Me)-NH.sub.2 or D-Agl(Me)-NH.sub.2. PA1 X-D-2Nal-(A)D-Phe-D-3Pal-Ser-Xaa.sub.5 -Xaa.sub.6 -Leu-Xaa.sub.8 -Pro-Xaa.sub.10 and the pharmaceutically acceptable salts thereof wherein: PA1 X is For, Ac, Acr, Pn, Bt, Vl, Vac, Bz or Q, PA1 Xaa.sub.5 is 4Aph(Q.sub.1) or 4Amf(Q.sub.1) with Q.sub.1 being Q or ##STR4## Xaa.sub.6 is D-4Aph(Q.sub.2), D-4Amf(Q.sub.2), D-Lys(Nic), D-Cit, D-Hci or D-3Pal, with Q.sub.2 being For, Ac, 3-amino-1,2,4 triazole, or Q.sub.1 ; PA1 Xaa.sub.8 is Lys(ipr), Arg, Har, Arg(Et.sub.2) or Har(Et.sub.2); and PA1 Xaa.sub.10 is D-Ala-NH.sub.2, NHCH.sub.2 CH.sub.3, Gly-NH.sub.2, AzaGly-NH.sub.2, Ala-NH.sub.2, Agl-NH.sub.2, D-Agl-NH.sub.2, Agl(Me)-NH.sub.2 or D-Agl(Me)-NH.sub.2. PA1 X-D-2Nal-(A)D-Phe-D-3Pal-Ser-Xaa.sub.5 -Xaa.sub.6 -Leu-Lys(ipr)-Pro-Xaa.sub.10 and the pharmaceutically acceptable salts thereof wherein: PA1 X is For, Ac, Acr, Pn, Bt, Vl, Vac, Bz or Q, PA1 Xaa.sub.5 is 4Aph(Q.sub.1) or 4Amf(Q.sub.1) with Q.sub.1 being ##STR6## Xaa.sub.6 is D-4Aph(Q.sub.2), D-4Amf(Q.sub.2), D-Cit, D-Lys(Nic) or D-3Pal, with Q.sub.2 being For, Ac, Q or Q.sub.1 ; and PA1 Xaa.sub.10 is D-Ala-NH.sub.2, NHCH.sub.2 CH.sub.3 or Gly-NH.sub.2. PA1 X-D-2Nal-D-4ClPhe-D-3Pal-Ser-Xaa.sub.5 -Xaa.sub.6 -Leu-Lys(ipr)-Pro-D-Ala-NH.sub.2 and the pharmaceutically acceptable salts thereof PA1 X is Ac or Q, PA1 MeCbm-D-2Nal-D-4Cpa-D-3Pal-Ser-4Aph(Hor)-D-Xaa.sub.6 -Leu-ILys-Pro-Xaa.sub.10 and the pharmaceutically acceptable salts thereof wherein D-Xaa.sub.6 is D-4Amf(Q.sub.1), D-4Aph(Q.sub.1) or D-3Pal,
Long-term GnRH-antagonist treatment (several months to many years) is expected to be effective treatment in the following indications;
Presently, the long period of treatment for these indications has been considered to require a sustained release GnRH antagonist depot preparation because daily sc injections are generally considered to be unacceptable. Linkage of GnRH analogs to cytotoxic radicals may increase the efficacy of cancer treatment using these compounds with a concomitant decrease of general toxicity.
The search for improved GnRH antagonists has resulted in the making of Antide, i.e. Ac-D-2Nal.sup.1, D-4ClPhe.sup.2, D-3Pal.sup.3, Lys(Nic).sup.5, D-Lys(Nic).sup.6, ILys.sup.8, D-Ala.sup.10 !-GnRH; and Cetrorelix, i.e. Ac-D-2Nal.sup.1, D-4ClPhe.sup.2, D-3Pal.sup.3, D-Cit.sup.6, D-Ala.sup.10 !-GnRH. U.S. Pat. No. 5,516,887 describes GnRH antagonists which are said to be more effective than Antide in suppressing plasma testosterone, e.g. Ac-D-2Nal.sup.1, D-4ClPhe.sup.2, D-3Pal.sup.3, D-N.sup..epsilon. -carbamoyl Lys.sup.6, Ilys.sup.8, D-Ala.sup.10 !-GnRH, which is referred to as Antarelix.
U.S. Pat. No. 5,296,468, issued Mar. 22, 1994, discloses the design and synthesis of a number of GnRH antagonists wherein the side chains of selected residues are reacted to create cyanoguanidino moieties, some of which subsequently spontaneously convert to a desired heterocycle, e.g. a 3-amino-1,2,4-triazole(atz). Such cyanoguanidino moieties are built upon the omega-amino group in an amino acid side chain, such as lysine, ornithine, 4-amino phenylalanine (4Aph) or an extended chain version thereof, such as 4-amino homophenylalanine (4Ahp). GnRH antagonists having such significantly modified or unnatural amino acids in the 5- and 6-positions exhibit good biological potency, and those built upon Aph are generally considered to be preferred. One that is especially preferred is Azaline B, i.e. Ac-D-2Nal.sup.1, D-4ClPhe.sup.2, D-3Pal.sup.3, 4Aph(atz).sup.5, D-4Aph(atz).sup.6, ILys.sup.8, D-Ala.sup.10 !-GnRH. U.S. Pat. No. 5,506,207 discloses biopotent GnRH antagonists wherein amino-substituted phenylalanine side chains of residues in the 5- and 6-positions are acylated; one particularly potent decapeptide is Acyline, i.e. Ac-D-2Nal.sup.1, D-4ClPhe.sup.2, D-3Pal.sup.3, 4Aph(Ac).sup.5, D-4Aph(Ac).sup.6, ILys.sup.8, D-Ala.sup.10 !-GnRH.
Despite the attractive properties of this group of GnRH antagonists, the search has continued for still further improved GnRH antagonists, particularly those which exhibit long duration of biological action. It can frequently be important that a peptide analog should exhibit a long duration of activity with respect to LH secretion, a property which may be enhanced by the peptide's resistance to proteolytic enzyme degradation in the body for both short-term and long-term treatment indications. In addition, to facilitate administration of these compounds to mammals, particularly humans, without significant gelling, it is considered extremely advantageous for such GnRH antagonistic decapeptides to have high solubility in water at normal physiologic pH, i.e. about pH 5 to about pH 7.4.